1. Field of the Invention
This invention relates to a process for the removal of sulfur dioxide from a gas mixture. More particularly, it relates to an improved process for the removal of sulfur dioxide from a waste gas stream in which the gas is scrubbed by an aqueous sulfite-containing scrubbing liquid.
2. Description of the Prior Art
Gas scrubbing methods are known and practiced commercially for the removal of sulfur dioxide from a waste gas stream. However, these methods are unsatisfactory, particularly from an environmental protection view, in that the effluent gas stream from a conventional process still contains an appreciable amount of sulfur dioxide. At least a partial solution could be obtained by adding one or more additional units of absorbing capacity to the process train. But this would put a rather substantial cost increase upon the process. A better answer to the problem would be to increase the efficiency of a conventional gas scrubbing process. Thus there is a need for an improved process for the economical removal of sulfur dioxide from a sulfur-dioxide-containing gas stream.
A reference which describes current practices in the removal of sulfur dioxide from a gas stream is the series of articles in the publication "Chemical Engineering Progress", August 1972, pp. 43-56. Other references include U.S. Pat. Nos. 3,607,001, 3,645,671 and 3,653,812.
The use of caustic as a scrubbing agent is discussed in U.S. Pat. No. 1,271,899 and British Patents 132,661 and 1427, of 1883.